A great amount of red mud generated from alumina production by Bayer process was considered as a low-grade iron ore with a grade of 5wt% to 30wt% iron. We adopted the reduction roastingmagnetic separation process to recover ferric oxide from red mud. The red mud samples were processed by reduction roasting, grinding and magnetic separating respectively. The effects of different parameters on the recovery rate of iron were studied in detail. The optimum techqical parameters were proposed with 700 ℃ roasting for 20 min, as 50wt% carbon and 4wt% additive were added. The experimental results indicated that the iron recovery and the grade of total iron were 91% and 60%, respectively. A novel process is applicable to recover ferric oxide from the red mud waste fines.

Soft starters are being used as induction motor starters in fan or pump drives, etc, the principle of which is based on the control of variable voltage and constant frequency. In the paper, we develop a kind of intelligent soft-starter for AC motors based on TMS320F240 digital signal processor (DSP). The method of designing the system that includes hardware and software is introduced. A new method of single neuron PI regulation is proposed to improve robustness and self-adaptation capacity of this system. It is proved by experiment that the system has excellent performance.

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The noise generated by hydrodynamic flow over an axisymmetric body with a flat nose is described quantitatively. Flush-mounted hydrophones were used to measure that part of the turbulent boundary-layer pressure fluctuations that propagates as true sound. Power spectra of sound pressure were measured in a 200-Hz to 150-kHz frequency range over a wide range of Reynolds numbers (U∞D/ν 2.52×10, where D is the diameter of the body) for the model operating in the China Ship Scientific Research Center 03B water tunnel. The power spectra of the noise measured in the laminar flow regions correspond little to those measured in the transition and fully developed turbulent regions of the flow. Free-stream turbulence intensity and transition regions on the model were measured by using a laser-Doppler velocimeter. The transition regions have been compared with the computation results and found to agree rather well with experiment. In addition to the experiment, 12 axisymmetric bodies are calculated and compared with the experiment. Results indicate that when the prismatic coefficient and DF/D are fixed, the model has fairly good flow properties. When DF/D is fixed and the prismatic coefficient is decreased, or the prismatic is fixed and the DF/D is decreased, the separation point or transition point is delayed.